Research is currently in progress on the mechanism of DNA replication in both procaryotes and eucaryotes. Studies on procaryotic DNA replication have centered on the interaction between the E. coli dnaA gene product and RNA polymerase and their role in the initiation of DNA synthesis. These studies utilize in vitro systems and a plasmid which carries the E. coli oriC region. Studies on eucaryotic replication have centered on the development of in vitro systems for the replication of the 2 microns DNA, the interfering nuclease activities, and the modifying activities present in the crude extracts used.